This interactive visualization displays health care spending in the United States by age group, gender, and payment source. A dropdown menu lets users select different expenditure categories, while the line chart animates between views using D3 transitions. The chart plots spending over time for total, male, and female populations, with a color legend distinguishing these groups. The visualization uses d3.csv, d3.scaleTime, d3.scaleLinear, d3.line, d3.nest, and d3.axisBottom/axisLeft to render SVG paths and axes, based on data from the Centers for Medicare & Medicaid Services.